Effect of 12-hour infusion of naloxone on mood and cognition in normal male volunteers.

The effects of a 12-hour naloxone infusion on mood, cognition, and plasma cortisol levels were evaluated in eight normal subjects. The dosage used was a 10 mg dose plus 7 mg/hr (total = 94 mg). Naloxone induced a significant rise in serum cortisol and also induced cognitive impairment, as shown by increased choice reaction time, reduced ability to recall the order of letters and numbers, and reduced accuracy of spatial orientation. The rise in cortisol induced by naloxone was significantly correlated with the rise in the Profile of Mood Scale (POMS) score, indicative of dysphoria. Finally, performance on the spatial orientation task was highly negatively correlated with the peak POMS score after naloxone. From these data and previous studies it is concluded that opioid receptors of low sensitivity to naloxone may mediate a common mechanism regulating the pituitary-adrenal axis' mood, and cognitive function during stress. Personality traits may account for the large individual variability reported in previous studies.